Ceres as seen by the Hubble Space Telescope. Image Credit: NASA/ESA/SWRI/Cornell University/University of Maryland/STSci
It takes Ceres 4.6 Earth-years to orbit the Sun, and 9 hours and 7 minutes to rotate around its axis. It is about 450 million km away from the Sun and formed in a cooler region of the early solar system than Vesta. For this reason, Ceres has a higher abundance of light elements and thereby a lower density. Due to the presence of water ice, possibly even liquid water, below the surface, Ceres shares some characteristics with comets. The water abundance is estimated to be between 17% and 27% by mass, and thus Ceres is considered “wet”. The surface has not yet been seen up-close, but images of the Hubble space telescope show variations in brightness that hint at morphological or chemical differences.
The expected inner structure of Ceres. Image Credit: NASA/ESA/STScI